Conventionally, a device that transmits energy by radio is known (for example, refer to patent references 1 to 3). This device is configured with a first resonator structure (resonance type transmission antenna) and a second resonator structure (resonance type reception antenna) located at a long distance from this first resonator structure. The first resonator structure receives energy from a power supply source (alternating current output power supply), and transfers the energy to the second resonator structure by using an electromagnetism resonance (magnetic field resonant coupling) without radiation. Further, the second resonator structure receives the energy from the first resonator structure and supplies this energy to an external load (reception circuit). Further, the resonance characteristic value Q1 of the first resonator structure and the resonance characteristic value Q2 of the second resonator structure are set in such a way as to satisfy the following equation (1).√(Q1·Q2)>100  (1)
As a result, the distance between the first and second resonator structures can be enlarged to be greater than its characteristic size (distance according to conventional electromagnetic induction) without reduction in the transmission efficiency of the energy.